Abstract: The existence of fast radio bursts (FRBs), a new type of cosmological
transients, has been established recently. The report of two FRB candidates
following two long Gamma-ray Bursts (GRBs) in a search for possible connection
between FRBs and GRBs, if confirmed in the future, will favor the origin of
delayed collapse of supramassive neutron star (SMNS) to a black hole. The
energy injected into the surrounding material by a SMNS will be in order of
1e52 erg unless the gravitational wave radiation is dominant. Energetic forward
shock will be driven and ultra-high energy cosmic rays can be accelerated.
Moreover, benefit from a very high rate of FRBs (i.e., 1e4 sky^-1 day^-1),
these ultra-high energy cosmic rays likely contribute significantly to the
observed ones. We also suggest that the mergers of double neutron stars, even
if they are irrelevant to FRBs, can play an important role in producing
1e18~1e20 eV cosmic rays if SMNSs were formed in a good fraction of mergers and
the merger rate is 1e3 yr^-1 Gpc^-3. Such a possibility will be unambiguously
tested in the era of gravitational wave astronomy.